; (>n PALEONTOLOGY OF NEW YORK. 



two species, in the ornamentation of the tube, form a small group, similar to 

 an assemblage of large and robust forms, named in the succeeding descriptions, 

 including C. Jason, G. spinosum and G. transversum. 



Formation and localities. In the Upper Helderberg limestone, Oneida and 

 Schoharie counties, and in the Helderberg mountains, Albany county, N. Y. 



Gyroceras paucinodcm. 



PLATS l.IV, FIGS. 1-4. 



Gyrorems (Hercoeeras f) paacinodus, Hall. Illustrations of Devonian Fossils : Cephalopoda, pi. 55, 



figs. 1-4. 1876. 



Shell discoid, closely coiled, making not less than two nearly contiguous volu- 

 tions. Transverse section triangular, ventral side the longest. The length 

 of the dorso-ventral diameter is about three-fourths of the lateral diameter. 

 Tube regularly and gradually enlarging from the apex to the aperture. 

 Apical angle about 7°. 



The extent of the chamber of habitation has not been observed. The 

 crenulations are preserved on the internal mould as fine, rounded striae. 

 Aperture slightly oblique, opening outward, with a distinct sinus on the 

 ventro-lateral margins, and in the middle of the ventral side. 



Air-chambers, septa and siphuncle unknown. 



The test has a thickness of about .5 mm. on the outer volution. Surface 

 marked by irregular slightly undulating lines of growth, curving in a retral 

 direction. The ventro-lateral angles are ornamented with a row of nodes 

 or spines, formed by the outward and backward bending of the lamellae of 

 growth. On the outer volution these nodes are separated by a distance of 

 about twenty-four mm., becoming more frequent toward the apex. Sinus 

 very broad and deep. 



The internal mould shows the furrows and striae of the crenulations, and 

 large rounded nodes on the ventro-lateral angles, corresponding to the 

 •xternal ornaments of the test. 



Three specimens have a uniform diameter of 100 mm. each, measured 

 across the disc, with a lateral diameter of forty-three mm. at the aperture. 



